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The limits associated with the use of linear momentum procedures in impact speed predictions of two-car collisions are well established. A combined linear and rotational momentum procedure is introduced which makes it possible to compute the impact speeds of each vehicle based on the post crash data of only one vehicle, or based on only the angles rotated of each vehicle. The limitations of the combined procedure are discussed. A speed sensitivity analysis is presented which offers a methodology by which reasonably accurate speed predictions can be made. A number of actual computer applications are shown which demonstrates the usefulness and simplicity of the procedure presented.

The Findings presented in this paper are based upon the investigation and reconstruction of more than 250 commercial vehicle accidents. Practical methods yielding acceptable results in terms of speed determination and fade and temperature prediction in truck run-away accidents are presented. The importance of accurate and complete data collection with respect to accident scene, mechanical condition of the vehicle, and driver human factors are discussed. The effects of complete, partial and no-wheel lockup on accident reconstruction are discussed for straight and out-of-control motion of the vehicle, including Jack-knifing. The importance of front wheel brakes is considered. The engineering concepts used in the analysis of accidents involving brake fade are presented including factors such as Jake brake, brake adjustment, and heat checking of drums. Driver factors are also considered. Truck rollover mechanics as it applies to braking accidents is reviewed.